As is known in the art, an electronic navigational chart is a three dimensional mathematical representation of part or all of a surface of the earth. An electronic maritime navigational chart typically includes hydrographical and topographical data such as water depth, shoreline locations, the existence of under water hazards such as rocks and islets, etc . . .
A particular area is often represented by a plurality of different charts, each of which represents the area or a portion thereof with a different scale. For example, the Port of Valdez, Ak. and the area thereabout is represented by a number of different charts at different chart scales including chart scales of 1:200,000, 1:40,000, 1:80,000, etc . . . Each of the charts provide hydrographical and topological information for a predetemined area in and around the Port of Valdez. Thus, a number of separate charts are often required to navigate a vessel in and around a particular area or port.
It is often necessary or convenient for a navigator to consult more than one chart substantially simultaneously. Thus when using paper charts, a navigator often concurrently views multiple charts in addition to other navigation aids such as floating aids to assist in navigating a vessel.
In the case of electronic navigational charts, the data for each chart is stored in separate data files. Thus, each time it is desirable or necessary to view a particular chart, a data processor must access the appropriate data file, read the data into a memory region of the data processor and display the data using appropriate image processing software. This process is often time consuming and computationally expensive. Furthermore, only one chart at a time at different scales can be viewed in such a manner. It is thus not possible to simultaneously view a plurality of different charts, each of which may be at different scales.
It would, therefore, be desirable to provide a system for combining a plurality of individual chart data files to provide a continuous chart database which allows viewing of multiple charts at different scales. It would also be desirable to provide a system for combining a plurality of individual chart data files in the DX90 data format to provide a continuous chart database which allows viewing of multiple charts at different scales.